Climate change and groundwater quality

Rather than being just water, groundwater always contains different substances dissolved from soil or bedrock. The concentrations of these substances are usually so low that they have no effect on using the water, but this situation may be altered by climate change.

The consequences of climate change may include greater fluctuations in groundwater levels. In winter, they are likely to be slightly higher than today, whereas in summer they can drop lower.

Such large variations will put groundwater quality at risk. As the water level drops, previously submerged soil layers come into contact with air which is always found between crumbs of soil. The oxygen in this air reacts with substances found in the soil, and some of them dissolve and seep into the groundwater. This chain of events may also be affected by soil microbes.

On the other hand, problems may also be caused if the groundwater level rises. Groundwater now starts flowing through soil layers that were previously above its surface and that may contain harmful substances which are released by the water.

Climate change may result in well water containing increased concentrations of iron and manganese as well as humus and other organic matter if heavy rains become more frequent and surface waters run into the well.

Extremely acidic sulphate soils in ancient sea bottoms are areas with a significant risk. Here a stable water table is crucial for maintaining good groundwater quality.